The use of fiber-optic cables to transmit digital data in local area networks, such as in office buildings is becoming increasingly more common. Some of the reasons for this phenomenon are the superior band width and superior transmission qualities of fiber-optic cables as compared to electrical wires made of copper or aluminum. In many installations, a plurality of cables are run to the same location. For example, in an office building, one end of a fiber-optic cable commonly terminates in a wiring closet along with possibly hundreds of other similar fiber-optic cables. The cables are run through the ceilings and walls of the building to various other termination points in the building, such as offices, cubicles, secretarial stations, or data stations elsewhere in the building. Even at these types of locations, there may be many fiber-optic cable ends for connection to office and data equipment. In most situations, most, if not all, of the cables will be essentially identical to each other in appearance. Accordingly, after the cables have been run from one or more locations to the same termination location, it is difficult for the installer of the cables to easily determine which of the many cables terminating at one location, corresponds to a particular cable end in the wiring closet. Accordingly, it is frequently necessary to input a light signal at one end of a cable and observe the ends of many cables to detect the light coming out of the other end of the cable in order to determine which cable termination point corresponds to which cable origination point.
Most commonly, to trace a fiber-optic cable run, an installer utilizes an ordinary flashlight with a specially designed adaptor for connecting to fiber-optic cable termination connectors. Particularly, he couples the flashlight to one end of the fiber-optic cable and then looks for the light coming out of the other end of the cable. This method of distinguishing fiber-optic cables from each other can be extremely difficult for several reasons. First, the incandescent, white, light generated by an ordinary flashlight is not particularly well focused or of particularly strong intensity. Further, the magnitude of the light is constant in time. Accordingly, it is sometimes very difficult to detect with the naked eye the light coming out of the opposite end of the cable because it is weak and of the same color as the ambient light in the room. Further, the cladding for many types of fiber-optic cables as well as the ferrule of most fiber optic connectors are white, i.e., the same color as the light, thus making it even more difficult to detect.
Many systems are known in the prior art for detecting a light input at one end of a fiber-optic cable at the opposite end of the fiber-optic cable. However, most of these systems are complex systems including both transmitting equipment and receiving equipment for, not only detecting the light, but also determining other properties of the cable. While these types of systems may be well adapted for certain applications, they are generally impractical, overly expensive, and overly complicated for the simple task of running cable through a building and distinguishing the various identical looking cables from each other.
U.S. Pat. No. 4,797,556 issued to Marzari et al. (hereinafter Marzari) discloses one such complex optical continuity testing apparatus comprising equipment for transmitting infrared test light pulses down a fiber-optic cable and separate receiving equipment for detecting the pulses at the opposite end. However, the light pulses are infrared and, therefore, are not detectable by the naked eye, but only by specifically designed receiving end equipment which then generates a visual and/or audible signal indicative of the power of the received light.
U.S. Pat. No. 4,870,269 issued to Jeunhomme (hereinafter Jeunhomme) discloses an optical fiber testing device using a pulsed laser diode. Again, this device is not designed for detection of the pulsed light by the human eye, but rather by specially designed detection equipment. In fact, the light transmitted down the cable under test is reflected back by "sensor" equipment positioned at the opposite end of the cable, and detected at the same end from which it was transmitted. Accordingly, this device assumes that the identity of the opposite ends of the cable is already known. Further, since it uses a laser diode to generate the transmitted light, it would be inadvisable to use the naked eye to detect the light output at the opposite end since it might be harmful.
U.S. Pat. No. 5,329,348 issued to Nimura (hereinafter Nimura) discloses a method for identifying a specific fiber-optic cable out of a number of similar optical cables. This patent pertains primarily to detecting fluctuations in the light transmissive qualities of the cable due to physical agitation of the cable at a point intermediate its two ends. Accordingly, this device is not designed nor practical for tracing cables at a construction site.
Therefore, it is an object of the present invention to provide an improved method and apparatus for tracing fiber-optic cables.
It is another object of the present invention to provide an inexpensive and simple method and apparatus for tracing fiber-optic cables.
It is a further object of the present invention to provide a method and apparatus for tracing cables using light signals that are easily detectable by the naked eye.